1. Technical Field
The present invention relates to a common mode filter and a method of manufacturing the same, and more particularly, to a common mode filter with the electromagnetic degree of coupling by implementing a primary coil and a secondary coil on a co-plane and making a length and a turn number of a coil equal and a method of manufacturing the same.
2. Description of the Related Art
As a demand for high-speed and multi-functional electronic devices increases, the use of an interface for high-speed data transmission has greatly increased. In particular, a high-speed interface based on a differential transmission scheme, for example, circuits, such as USB 2.0, USB 3.0, HDMI, and the like, has increasingly used a filter for removing a common mode noise and the development of a small-sized and high-performance common mode noise filter (CMF) capable of coping with a trend of the use of a high frequency and the miniaturization of components is very urgently required.
In order to improve electrical characteristics of coil components such as a common mode filter (CMF), and the like, it is important to increase the electromagnetic degree of coupling between the primary coil and the secondary coil. In order to increase the electromagnetic degree of coupling between the primary and secondary coils, there is a need to form a magnetic path so as to reduce an interval between two coils or prevent a leakage flux from occurring. However, in an SMD type, a terminal unit for mounting is biased to each corner, such that a structure in which an inter-coil matching relationship is not formed appears. In other words, a difference in an inter-terminal distance occurs, such that a difference in an impedance value, a difference in a length of a conducting wire, a difference in a turn number of a magnetic core (a central magnetic path) cannot but occur and terminal impedance of two coils, respectively, cannot be equally formed structurally. Therefore, there is a problem in that an insertion loss may be degraded with the reduced electromagnetic degree of coupling between two coils.
In the related art, an inter-terminal impedance difference is compensated by biasing a starting position of a coil to one side in order to compensate for the inter-coil turn number by using a compensation method. However, even in this case, there is the inter-terminal impedance difference, for example, the impedance difference of a minimum of about 8%. Further, even when the compensation is performed by biasing the central magnetic path (magnetic core) from a center to one side and biasing the coil to one side, the inter-coil impedance difference of a predetermined amount, for example, a minimum of about 5% occurs.